A bill that would allow children with severe epilepsy to obtain an oil extracted from marijuana to help control their seizures has moved to the floor of the state Senate.

However, a major change could prevent the bill from helping the child who inspired it.

On Thursday, the Senate Medical Affairs Committee approved the bill, which would allow doctors to administer cannabidiol to patients with intractable epilepsy, but with one major revision: The CBD oil administered must be approved by the Food and Drug Administration and be part of clinical trials.

If passed in its current form, the restrictions placed in the revised bill would prohibit 6-year-old Mount Pleasant resident Mary Louise Swing, whose illness prompted the bill’s introduction, from receiving CBD oil in South Carolina, Swing’s mother, Jill, said. The only FDA-approved drug currently being used for trials, Epidiolex, is restricted to two forms of epilepsy that do not include Mary Louise’s condition, Jill Swing said Monday.

S.C. Sen. Tom Davis, R-Beaufort, introduced the bill in February after meeting Mary Louise’s grandmother, Harriett Hilton of Beaufort, who told Davis about her granddaughter’s condition. Mary Louise takes two medications but still suffers between 20 and 60 seizures an hour. Without medication, those numbers can jump to 200 seizures an hour.

Davis said the change was made at the committee level because of concerns raised by the S.C. Medical Association and the State Law Enforcement Division about the quality and purity of the CBD oil. However, he plans to introduce an amendment that would allow doctors and physicians to prescribe the oil directly.

That would allow children like Mary Louise to receive the oil without participating in restrictive clinical trials.

Davis could file his amendment as soon as Wednesday. He said the bill is scheduled to be read todayTuesday; after a 24-hour waiting period, Davis can introduce the amendment and a vote can be taken on the bill.

Davis said he also is working with U.S. Sen. Lindsey Graham to set up the Medical University of South Carolina as a testing site for FDA-approved CBD oil. The bill would create a therapeutic research program for cannabidiol oil within the S.C. Department of Health and Environmental Control, but MUSC still needs federal approval to administer it.

Davis said Monday he was optimistic the amendment would pass the Senate. Jill Swing said she hoped the bill could be broadened further to include “compassionate use,” which allows patients to receive drugs that have not yet gained FDA approval outside of a clinical trial to assess their effectiveness.

People can be eligible for the program if they don’t qualify for clinical trials or if approved treatments haven’t helped their condition. Swing said one of the medications her daughter had previously used was obtained through the compassionate-use program, but the revised bill could cut off future access to similar avenues.

Swing was one of the parents who testified at a subcommittee hearing last week. There she met another family who moved to Colorado, where CBD oil is legal, in a last-ditch effort to get treatment for their daughter’s seizures.

Swing said moving across the country to help her daughter’s condition — far away from her husband, Mary Louise’s twin brother and the majority of their extended family — might become an option for her family, as well.

“It’s probably going to happen if these changes aren’t made or the bill doesn’t pass,” she said. “It’s still a big topic of conversation in our household. Mary Louise’s seizures aren’t life-threatening like others are, so we have some more time to decide. If I was in that situation, we’d be there already.”